Drywall also commonly known as Gypsum Board is a common manufactured building material used globally for the finish construction of interior walls and ceilings

A drywall panel is made of paper liner wrapped around an inner core made primarily from gypsum plaster, the semi-hyfrous form of calcium sulphate. The raw gypsum is calcined before use.

The plaster is mixed with fiber, (typically paper and/or fiberglass), foaming agent, various additives that increase mildew and fire resistance and water and is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats.

When the core sets and is dried in a large drying chamber, the sandwich becomes rigid and strong enough for use as a building material

As opposed to a week-long plaster application, an entire house can be drywalled in one or two days by two experienced dry liners.

The boards are cut to size by using a large T-square by scoring the paper on the front side with a utility knife, breaking the sheet along the cut, scoring the backing and finally breaking the sheet in the opposite direction. Small features such as holes for outlets and light sockets are usually cut using a keyhole saw or a small high speed bit in a rotary tool.

Drywall is then fixed to the wall structure with nails or more commonly the now-uniquitous drywall screw

After the sheets are secured to the wall studs or ceiling joists, the seams between drywall sheets are concealed using joint tape and several layers of joint compound. Paper Tape or Fibre Tape may be used. Some architects prefer a skim coat over the whole surface which is currently the prefered method of Cull Dry Lining & Plastering.

Drywall screws have a curved bugle shaped top, allowing them to self pilot and install rapidly without punching through the paper cover. These screws are set slightly into the drywall. When drywall is hung on light gauge steel framing, screws having a acute point and finely spaced threads are used. If the steel framing is heavier than 20-gauge, self tapping screws with finely spaced threads must be used.

This compound is also applied to any screw holes or defects. The compound is allowed to dry then typically sanded smooth before painting.

When used as a component in fire barriers, drywall is a passive fire protection item, subject to stringent bounding. In its natural state, gypsum contains the water of crystallisation bound in the form of hydrates.

When exposed to heat or fire, this water is vapourised, retarding heat transfer.

Therefore, a fire in one room, which is separated from an adjacent room by a fire resistance rated assembly will not cause the adjacent room to get any warmer that the boiling point (100.c) until the water in the gypsum is gone.

This makes drywall and ablative material because as the hydrates sublime, a crumbly dust is left behind, which, along with the paper is sacrificial.

Waste

Because up to 17% of drywall is wasted during the manufacturing and installation process, and the drywall material is rarely re-used, disposal is an ongoing problem.

Cull Dry Lining & Plastering are committed to ensuring all drywall waste is disposed of only by specialist waste contractors